The present invention relates to a down hole cleaning apparatus and method for removing debris that is clogging the perforations of an oil well and for bailing liquid from a well.
The perforations at the bottom of wells frequently become blocked or clogged by particulate debris such as sand or fractured concrete. This debris can damage well equipment and it impedes the flow of oil into the well, therefore it is important to remove the blockage as quickly and efficiently as possible. Conventional practice to remove blockages involves the use of a down hole cleaning tool lowered into the well on a wire or sinker bar. Such tools often have a means for engaging the walls of the well to form a tight seal and generally rely on fluid pressure or suction to dislodge the debris from the perforations into the main well bore. The cleaning tool is lowered to the proximate depth of the blockage and is then activated. Upwards motion of the tool creates suction which may unblock the perforations.
Once the debris has been drawn into the main well bore, the suspended debris must be removed to prevent further interference with the operation of the well. This phase of the procedure involves the use of a bailer apparatus which is usually comprised of a length of valved tubing that is lowered into the well, commonly on a wire, and which is then withdrawn full of liquid. This procedure is repeated until the desired amount of liquid and suspended debris has been removed from the well.
A conventional prior art cleaning device cannot be used concurrently with a bailer. This greatly slows down the entire cleaning and bailing process, making it a more labour intensive operation because after the cleaning operation is completed, the cleaning apparatus must be withdrawn from the well and removed from the wire before the bailer can be substituted onto the wire and lowered into the well. If more cleaning is required after a period of bailing, the whole replacement procedure must be repeated.
Some prior art cleaning devices are designed to be attached to the end of bailers, but these prior art cleaning devices are frequently mechanically complex having numerous parts and they often rely on intricate spring loaded valve systems. This complexity elevates the possibility of mechanical failure and increases the cost of manufacture and repair. Further, such tools are generally not designed to facilitate bailing; rather they are only functional for the cleaning phase of the operation. To commence bailing following cleaning, the cleaner must be removed from the end of the bailer, the bailer must be re-configured for bailing operations and then the bailer must be reinserted into the well. This can reduce the efficiency and speed of the cleaning and bailing process.
Therefore there is a need in the art for a cleaning tool that can be used with a bailer and that can be used to bail liquid from the well, but that can also be adjusted to disengage the well wall once the debris has been dislodged from the perforations.